Carbon and carbon-containing nanotubes are unique carbon-based, molecular structures that exhibit interesting and useful electrical properties. There are two general types of carbon nanotubes, referred to as multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs). SWNTs have a cylindrical sheet-like, one-atom-thick shell of hexagonally-arranged carbon atoms, and MWNTs are typically composed of multiple coaxial cylinders of ever-increasing diameter about a common axis. Thus, SWNTs can be considered to be the structure underlying MWNTs and also carbon nanotube ropes, which are uniquely-arranged arrays of SWNTs.
SWNTs are ideal quantum systems for exploring basic science in one-dimension. Molecular-scale SWNTs, derived by bottom-up chemical synthesis approaches, are also promising as core components or interconnecting conductors for electronics, tips for atomic force microscopy (AFM) and other applications. When isolated, individual nanotubes are particularly useful for making microscopic electrical, mechanical, and electromechanical devices.
Obtaining individual, high quality, single-walled nanotubes has proven to be a difficult task. Existing methods for the production of nanotubes, including arc-discharge and laser ablation techniques, yield bulk materials with tangled nanotubes that tend to be mostly in bundled forms. These tangled nanotubes are extremely difficult to purify, isolate, manipulate, and use as discrete elements for making functional devices. AFM probe tips, for example, are sized and shaped in a manner that affects the lateral resolution and fidelity of AFM images.
The above-mentioned and other difficulties in mass-producing carbon nanotubes have presented challenges to the implementation of such nanotubes in a variety of applications.